The present invention relates to a clock-synchronously operated electronic circuit, and particularly to a clock-synchronously operated semiconductor integrated circuit, and relates to a technique effective when applied to an information processing apparatus typified by a microcomputer, for example.
As a semiconductor integrated circuit such as a clock-synchronously operated microcomputer, there is known one wherein a synchronous clock signal is generated by internal oscillations alone without external attachment of a crystal oscillator (crystal unit, crystal oscillation). A microcomputer, which generates a synchronous clock signal by only internal oscillations without externally providing a crystal oscillator, has been described in the following patent document 1. A circuit, which trims the oscillation frequency of a built-in oscillator that internally oscillates, without external attachment of a crystal oscillator, has been described in the following patent document 2.
Patent Document 1    Japanese Unexamined Patent Publication No. Hei 11(1999)-510938
Patent Document 2    Japanese Unexamined Patent Publication No. Hei 10(1998)-187273